In an effort to minimize the fear, risk, and pain associated with needle injections, several types of needleless methods of drug delivery have been developed. These methods focus on delivering drug through the skin in a variety of different ways (e.g., passive or active diffusion utilizing patches, thermoporation, ultrasound or other energy sources, etc.). However, not all of these methods are effective for delivering all types of drug across and/or through the skin, given its significant and protective barrier function. To be sure, penetrating the skin barrier has proven challenging at times because of its low permeability to foreign molecules, especially large molecules. The main barrier to entry of these molecules is the outermost layer of skin, or the stratum corneum, which consists of densely packed keratinocytes (flat dead cells filled with keratin fibers) surrounded by lipid bilayers, which are highly ordered.
To overcome the barrier function of skin, the present Applicants have developed several microjet injectors that are capable of delivering drugs across the skin surface in a non-invasive fashion, see, e.g., U.S. patent application Ser. Nos. 10/829,888 and 11/367,202 each of which are incorporated herein by reference in their entirety. Other microjet devices have also been described.
Given the advantages microjets offer over standard needleless methods of drug delivery, improvements in the microjet art would be desirable. For example, microjet devices that maximize entry of drug into the skin (or prevent leakage of the drug therefrom) would be desirable. Similarly, microjet devices that are easy to use would be desirable.